Last year, Congress passed an amendment that barred the Department of Justice from using federal dollars to prosecute medical marijuana dispensaries in states that have legalized them. Last week, three senators proposed a measure to clean up the federal-state medical marijuana mess once and for all.

Sens. Cory Booker, D-N.J., Kirsten Gillibrand, D-N.Y., and Rand Paul, R-Ky., introduced their Compassionate Access, Research Expansion and Respect States Act, which should draw support from the right and left. Why? First, it would reclassify marijuana from a Schedule I drug to a Schedule II, granting recognition that marijuana has legitimate medical uses, a sop to the left. Second, it would direct the federal government to stop prosecuting dispensers in states that have legalized marijuana for medical use — a states' rights emphasis that should draw GOP votes. The measure also would allow cannabidiol imports to help patients with epilepsy and seizure disorders — the folks who need medical marijuana the most — and allow Veterans Affairs doctors to prescribe medical marijuana. Booker sees his legislation as a matter of "common sense, fiscal prudence and compassion."

For decades, Congress wouldn't move on medical marijuana because D.C. pols thought of advocates as goof-offs who just want to get high. They didn't see the legitimate medical benefits. Then, two years ago, CNN physician-reporter Sanjay Gupta looked at the issue anew and found that cannabis could help children with life-threatening seizures. Medical marijuana has been used to treat people with epilepsy, Parkinson's disease, brain tumors and post-traumatic stress disorder without the serious side effects often associated with prescription drugs.

From San Francisco, the CARERS Act looks like a political slam-dunk. It has bipartisan support. Already 23 states have legalized medical marijuana, which puts momentum on the "yes" side. "It stands a good chance of moving because it's so bipartisan in nature," said Bill Piper, the Drug Policy Alliance's man in Washington, D.C. But: "The hard part is going to be getting it through committee." Senate Judiciary Committee Chairman Chuck Grassley, R-Iowa, opposes the bill.

Will Grassley allow the bill to come to a vote? "The committee is unlikely to take up a bill in the near future that remakes these laws so broadly," spokeswoman Jill Gerber answered. She added that Grassley "is looking at ways to lift any unnecessary barriers" to scientific research into marijuana-based medicines to treat epilepsy and other conditions affecting children.

There are 11 GOP and nine Democratic senators on the committee. I see three R's who could vote yes; Mike Lee of Utah and Ted Cruz of Texas support states' rights, and Jeff Flake of Arizona voted for similar legislation in the House. Maybe I'm wrong. Maybe there are more.

That would put Sen. Dianne Feinstein in the middle. Other committee Dems are very likely to vote yes. On the one hand, Feinstein and Grassley often work closely on drug war issues. On the other hand, Feinstein does represent California. Her office told me DiFi is still reviewing the legislation.

Which leads to my final question: Would President Barack Obama sign the CARERS Act? Advocates believe that the White House could have and should have made marijuana a Schedule II drug years ago but didn't. The administration has been behind the curve. "Everyone pretty much believes that" Obama is not really for current federal marijuana laws, said Marijuana Majority Chairman Tom Angell, just as many believed Obama supported same-sex marriage back when he said he was against it. "I wouldn't be shocked to see him evolve on this issue the same way he did for marriage equality," Angell mused. "Maybe all we need is for Joe Biden to say that marijuana should be legal."